1. Field of the Invention
The present invention relates to water-based coating remover compositions, and concentrates from which said compositions are made for removing coatings from wood substrates.
2. Description of Relevant Art
The removal or stripping of paint, varnish, lacquer and other coatings or finishes from a surface is generally very complex presenting a variety of problems to those in the art. Factors which influence a particular stripping operation include: the type of coating(s); thickness of the coating(s); type of substrate the coating is on; whether a primer was used and if so the type and thickness of primer; the type of pigment; the curing time, temperature and method; and the age of the coating.
As paint and other coating formulations improve, it becomes increasingly difficult to remove these coatings from a variety of surfaces and in a variety of situations. Such situations range from large industrial operations to a hobbyist refinishing a piece of furniture. The coatings to be removed range from old oil-based paints to highly polymerized modern coating materials which, by design, are increasingly resistant to chemical removers. Desirable properties and characteristics for a coatings remover includes: stripping ability (effectiveness); be noncorrosive to the substrate; will not promote galvanic attack at the juncture of different metals; free of noxious and toxic chemicals; good shelf life; low volatility; leave a substrate ready for further processing; and be low in cost.
The Known coating removers used for removing coatings from wood substrates contain large percentages of methylene chloride and/or highly flammable solvents, or are caustic or acid solutions. Products currently used by professionals do not lend themselves to relatively safe use by the general public. Although substantially the same disadvantages are encountered by both professionals and the general public, these disadvantages are more acute with respect to the general public. Such disadvantages include toxicity, flammability, volatility, non- or inadequate biodegradeability and difficult to apply and/or remove.
Alternative constituents to methylene chloride, particularly in formulations intended for consumer (general public) purchase, typically increase the cost to such an extent that such formulations cannot effectively compete with methylene chloride containing formulations.
A non-methylene chloride containing paint stripper is disclosed in U.S. Pat. No. 4,666,626 which generally discloses a non-methylene chloride paint stripper composition containing oxo-hexyl acetate as the chief cleaning agent in combination with cyclohexanone. The compositions preferably also contain furfuryl alcohol, an aromatic naptha solvent, methyl cellulose thickener, dodecyl benzene sulfonate, N-methyl-2-pyrrolidone, diisobutyl ketone and sodium xylene sulfonate. It is also stated the composition readily emulsifies with water and is removable by water.
Although N-methyl-2-pyrrolidone is known for use primarily as an activator or cosolvent in certain paint, varnish and other coating removers, it is also known for use as an active solvent in some coating remover formulations.
In U.S. Pat. No. 4,120,810, a paint remover composition consisting of a mixture of 15-60 mole percent NMP and 35 or more mole percent of an aromatic hydrocarbon solvent consisting of a mixture of aromatic hydrocarbons having more than 6 carbon atoms is disclosed. Also disclosed as optional ingredients are high flash point glycol ethers (up to 50 mole percent), from one to six percent of a cellulose thickener, and a surfactant to improve water washability. Although effective as a paint remover, stripping formulations based on this reference present certain disadvantages. Commercially available formulations did not rinse well with water leaving behind a white haze on the substrate believed to be precipitated thickener. The cost of these formulations is high particularly when compared to methylene chloride based removers. There is a high volatile organic material content to these formulations which causes environmental concerns particularly regarding disposal of spent remover. The disclosure states that water should not be used as a constituent of those formulations.
In U.S. Pat. No. 2,918,443, a solvent for use in applying resins consisting of copolymers of vinyl chloride and vinyl acetate in certain proportions is described, said solvent consisting of 7 to 95 percent by weight N-aliphatic hydrocarbon substituted derivatives of 2-pyrrolidone having no more than four carbon atoms in the aliphatic carbon group and a liquid mono nuclear aromatic hydrocarbon. There is no disclosure or suggestion of several of the constituents of the present concentrate or water-based formulation or that such constituents could be used to afford a stable water-based coating remover composition.
In U.S. Pat. No. 4,085,059, a liquid coating remover, particularly for polyamide epoxy resin type coatings, adapted for forming a relatively stable foam is disclosed. This coating remover consists of 5-35 percent by weight N-methyl-2-pyrrolidone (NMP), 10-35 percent by weight water-soluble organic surfactant blend capable of emulsifying a gas, and 30-85 percent by weight water. The surfactant blend is said to consist of a mixture of 5-15 percent by weight C.sub.6 -C.sub.18 fatty acid material, 3-10 percent by weight alkylolamines and 5-15 percent by weight polyhydric alcohols, all amounts based on the total weight of the composition. Applicant's invention includes constituents which are not disclosed or suggested by this reference. Unlike the present invention, the reference uses a blend of at least three surfactants and is adapted to form an emulsion with a gas; that is a foam.
In M-Pyrol Bankbook, GAF Corporation, 1972, pages 51-52, discloses two paint remover formulations that include N-methyl-2-pyrrolidone. The first formulation includes NMP at 56.5 parts by weight and methylene chloride at 30 parts by weight along with a particular anionic surfactant at 10 parts by weight, paraffin wax at 1.5 parts by weight and Methocell.RTM. HG (hydroxypropyl methylcellulose thickener commercially available from the Dow Chemical Company) at 2.0 parts by weight. The present invention does not include methylene chloride or paraffin wax and does include other constituents.
The second formulation consists of NMP at 98.5 parts by weight, di-2-ethylhexylamine at 0.75 parts by weight and Carbopol.RTM. 934 resin (commercially available from B. F. Goodrich Chemical Co.). The high cost of such a formulation because of the large NMP concentration renders such a formulation quite unattractive.
A brochure available from The Dow Chemical Company entitled METHOCELL 311 Cellulose Ether (form no. 192-1040-87) described viscosification properties of METHOCELL 311 (commercially available from the Dow Chemical Company) in various methylene chloride/alcohol systems. It also described viscosification properties of METHOCELL 311 in four non-methylene chloride paint stripper formulations. All formulations include toluene at 23.5 percent by weight, methyl alcohol at 19.0 percent by weight and METHOCELL 311 at 1.0 percent by weight. Test formulation 1 includes NMP at 55 percent by weight. Test formulation 2 includes acetophenone at 55 percent by weight. Test formulation 3 includes tripropylene glycol monomethyl ether at 55 percent by weight. Test formulation 4 includes a mixture of tripropylene glycol monomethyl ether and acetophenone, each at 27.5 percent by weight. All of these formulations require the presence of methyl alcohol which is undesirable due to its toxic effects on humans.
In U.S. Pat. No. 4,780,235 a low toxicity paint remover composition is disclosed consisting of at least 20 percent by weight of at least one C.sub.1 -C.sub.4 dialkyl ester of a C.sub.4 -C.sub.6 aliphatic dibasic acid; 0.1 to 5 percent by weight of an activator, an effective amount of a thickener; an effective amount of a compatible surfactant; and from 1 to 80 percent by weight of at least one nonhalogen-containing organic solvent. The present invention does not include an activator, more particularly the basic or acidic activators described in the patent. Further, the surfactant is said to be present to enhance the water wash of the substrate. There is no suggestion regarding water-based coating remover compositions.
Despite the above and other alternatives to methylene chloride type removers, there continues to be a need for coating removers having equivalent or improved performance to the known removers at lower cost.
Accordingly, one object of the present invention is to provide a coating remover composition, particularly for coatings of the type used on wood substrates such as lacquers, varnishes, enamels, latex and one part moisture cure urethanes, that is of reduced toxicity.
Another object is to provide a coating remover that is composed of high flash point constituents and exhibits low skin irritation.
A further object is to provide a coating remover having reduced volatile organic material content while being effective and has a good shelf life.
Still a further objective is to provide a coating remover that does not raise the grain of wood substrates during use and which allows equipment to be cleaned with water, following use.